DE2426698A1 - Highly silanised silica carriers for gas chromatography - prepd by hydration and solventless treatment with silanol - Google Patents

Abstract

Silanisation of carrier materials (I) based on SiO2 by treatment with silanols comprises (a) hydrating (I) with water or steam; (b) treating with silano(s) of formula RR'2SiOH, (II), (in which R is 1-25C alkyl or alkoxy, in which >=1 non-adjacent CH2 gps. are replaced by O, or Ph; the R' gps. independently are Me or Et) in the absence of a solvent at 50-450, pref. 80-150 degrees C, opt. in the presence of a volatile base, pref. NH3, and (c) removing excess (III). The mat. of (II) used pref. is 10-30 mu mole/m2 surface area of (I). Treatment with (II) pef. takes place in a closed system. Method is esp. for the prodn. of carrier materials for stationary phases is gas chromatography. A relatively high degree of silanisation is achieved.

Description

Process for the production of silanized carrier materials The invention relates to a new process for the silanization of carrier materials Silica base.

The use of porous inorganic adsorbents, especially of Silicon dioxide, as a carrier material for catalysts or for partition chromatography, especially for gas chromatography and column liquid chromatography, is known. Because of their high activity, such carrier materials are suitable for many separation problems as well as for some catalysts only suitable to a limited extent. There are therefore many attempts have been made to standardize the surface of silicon dioxide to change. By varying the pore structure, the chroinatographic Behavior of the silicon dioxide can also be influenced; the disturbing influence however, the surface silanol groups can only be modified by means of a modification the surface can be reduced with organic or organosilicon reagents. The treatment of the surface with organosilicon reagents, the general is referred to as silanization, is due to the comparison to Si-O-C bonds higher temperature and hydrolysis resistance of the surface brought Si-C bonds preferred. The Si-O-Si bonds made during silanization are also sensitive to hydrolysis; However, if the surface layer with the Si-C bonds is very dense, it protects the underlying Si-O-Si bonds. It is therefore desirable to be as dense as possible Surface layers with Si-C bonds.

It is known that untreated support materials based on silicon dioxide contain a maximum of about 7 micromoles of silane groups on one square meter of their surface.

In the case of the silanization processes known from the literature, also using of very reactive organosilicon reagents such as chlorosilanes or hexamethyldisilazane, but it has regularly been found that only about 2.5 -3 Micromol / m2 of the existing silanol groups are implemented. From this it was concluded that for steric reasons only with low molecular weight silanization reagents about every second silanol group, that is 2 maximum 3.5 micromol / m, can react. The undesirable influence of the silanol groups not converted in the silanization reaction one tries to eliminate or at least reduce that as silanization reagents Such organosilicon compounds are used by the space filling at least one of the Substi'Luentel; on the silicon atom these silanol groups sterically shield.

For this type of silanization of carrier materials based on silicon dioxide several procedures have already become known.

In a particularly preferred process, the carrier material to be silanized is treated with a halosilane, usually a chlorosilane of the general formula Ia wherein Hal is a halogen atom, preferably chlorine, and R3, R4 and R5 are organic radicals, reacted.

In this case, 1 mol of hydrogen halide is used for every 1 mol of the converted halosilane free. This method is therefore only suitable for silanizations that are under absolute anhydrous conditions can be performed. This is particularly technical Scale associated with great effort, which makes the process economically viable burdened.

In the presence of water, hydrogen halide is formed from the halosilane and disiloxane. As a result, on the one hand the reagent is lost, on the other hand the Hydrogen halide formed is corrosive.

When the implementation of silica substrates with halosilanes of the formula Ia in an anhydrous, inert organic solvent, if appropriate in the presence of an acid-binding agent, are carried out largely obtain uniform reaction products; however, there are clearly fewer silanol groups of the carrier material reacted with the halosilane than in the absence of a solvent.

In another silanization process, the carrier material to be silanized is coated with an alkoxysilane of the general formula ob R3 4th Alk-O-Si-R4 Ib R. wherein Alk is a lower alkyl radical, preferably methyl or ethyl, and R3, R4 and R5 have the meaning given in formula Ia, reacted. In this reaction, interference by the by-products of the reaction is excluded; it turns out, however, that the degree of conversion is generally too low to achieve the desired effect of binding or shielding all of the silanol groups of the support material. This is attributed to a relatively firm adsorption of alkoxysilane molecules on the carrier material, where these prevent further alkoxysilane molecules from reacting completely with the silanol groups. However, the adsorbed alkoxysilane molecules are not bound tightly enough so that they cannot be removed again by heating or contact with eluents. In the process, the silanol groups, the undesirable effects of which are just about to be eliminated, are exposed again.

Furthermore, attempts have already been made to use silicon dioxide carrier materials in the presence of inert organic solution with silanols of the general formula Ic in which R3, R4 and R5 have the meaning given in formula Ia. Here, too, the degrees of conversion achieved were too low for the desired purpose.

The present invention was based on the object of a new and improved process for the silanization of carrier materials based on silicon dioxide to find.

According to the invention, this object is achieved in that the carrier material is hydrated by contact with water or steam, an excess of one or more silanols of the general formula II where R1 and R2 are identical or different and are methyl or ethyl, and R is an alkyl or alkoxy group with 1-25 C atoms, in which case one or more non-adjacent CH2 groups have been replaced by oxygen atoms, or a phenyl group means, allowed to act in the absence of a solvent at a temperature between 50 and 450 ° C., optionally in the presence of a volatile base, and then wntfernet the excess silanol in a well-known way. In this way, 2.8 micromoles / m2 of the surface silanol groups of the carrier material are etherified with an organosilicon group.

From Izvestia Akademii Nauk SSSR, Neorganicheskie Materialy, volume 6 (1970), pages 59-62, a process is already known in which silicate Materials have been treated with silanols. Chrysotile asbestos, Muscovite and talc, which were dehydrated at 3750C and 200 ° C, respectively, in boiling m-xylene reacted with silanols such as triethylsilanol, triphenylsilanol or methyldiphenylsilanol. In comparative tests it was found that with this method a much lower Part of the surface silanol groups of the carrier material with the silanol of the general formula II reacts as in the process according to the invention.

This result appears surprising in particular because too would have been expected, since the water formed in the reaction with the boiling organic solvent removed from the reaction site by azeotropic distillation is, the equilibrium of the silanization reaction towards the formation of the silanized carrier material is moved. In the method according to the invention, that in one preferred embodiment in a closed Vessel is carried out is the removal of the water formed in the reaction naturally not possible; nevertheless, there are significantly higher degrees of silanization achieved. The same degree of conversion is achieved even when water is added to the reaction mixture achieved.

According to the method according to the invention, both artificial and natural carrier materials based on silicon dioxide can also be silanized. As-natural Carrier materials are in particular kieselguhr, sand, talc and mineral silicates such as muscovite or chrysotile asbestos. Particularly suitable artificial ones Carrier materials based on silicon dioxide are, for example, silica gel, glass, ceramic materials, porous glasses that are either porous through and through or only on the surface have a porous structure up to a limited depth and are finely divided Silicon dioxide, for example by flame hydrolysis of silicon tetrachloride will be produced. Kieselguhr, silica gels and, in particular, those obtained by flame hydrolysis Finely divided silicon dioxide are preferred in the context of the present invention Carrier materials based on silicon dioxide.

Preferably, according to the invention, carrier materials with 2 one specific surface area of more than 100 m per gram, especially those with a Surface of 150 - 300 m2 per gram silanized.

The process according to the invention is generally carried out as follows: Before the reaction with the silanols of the general formula I *, the is to be silanized Carrier material initially through a Treatment with water or steam hydrated.

In the context of the present invention, hydration is a Treatment of the support material understood through which the number of surface Silanol groups is brought to a maximum. For example, you can do this Carrier material for a sufficiently long time, for example 1 - 200 hours in an aqueous one Stand slurry.

The hydration can take place at room temperature, but it can also for acceleration or intensification at elevated temperature, for example done by boiling with water. Occasionally it can be useful to add the water catalytic amounts, for example 0.1-10 percent by weight, of a strong mineral acid like adding hydrochloric acid or sulfuric acid. Optionally, the carrier material also by treatment with water or steam under increased pressure at temperatures above 1000C, for example in an autoclave at 200-4000C. at For some carrier materials, leaving them to stand for a long time in water vapor-saturated ones is sufficient Atmosphere at normal pressure or reduced pressure to ensure sufficient hydration bring about. Allowing to stand is used to hydrate glass surfaces concentrated nitric acid is preferred, which is also the surface Dissolves cations.

The support material hydrated in this way becomes, if hydrated an acid was added, first washed acid-free and then expediently through freed from adhering water in a drying step. In principle, according to the invention also an air-dried hydrated carrier material with a silanol of the formula II are implemented; however, in this case there is a slightly larger excess of the silanol II than in the conversion of dried material to achieve an equally high degree of silanization. It has therefore been found to be beneficial proved to dry the hydrated material beforehand to such an extent that though the number of silanol groups is not reduced again by splitting off water, but adherent free, adsorbed or chemisorbed by hydrogen bonding Water is at least partially removed again. A shower drying will for example, by gently heating the hydrated carrier material at reduced Pressure achieved; however, the temperature should not exceed 50-90 ° C. if possible.

The carrier material so hydrated is then in the absence of one Reacted solvent with a silanol of the general formula II. In the silanols of the general formula II, the groups R1 and R denote methyl and / or ethyl groups. Because of their simpler producibility, preference is given to silanols in which groups R1 and R2 are the same. The R-dimethylsilanols are particularly preferred of the general formula II, as they are easily obtained from the commercially available dimethyldichlorosilane can be produced. The group R can be an alkyl or alkoxy group with 1 - 25 C atoms mean, in which one or more non-adjacent ClI2 group (s) - with Alko = y groups R also not the oxygen atom bound to the silicon atom adjacent CH2 group - can be replaced by oxygen atom (s). The selection of the radical R is important for the process according to the invention only insofar as if appropriate, the reaction temperature and thus the reaction time accordingly the thermal sensitivity of this group must be selected. Incidentally, the The remainder R corresponds to the intended use of the silanized carrier material to be selected. So it is useful to use carrier materials that come into contact with little polar organic solvents such as gasoline, paraffin or benzene should come through implementation with to silanize such silanols, in which the group R is an alkyl group without breaking the carbon chain Is oxygen atoms. In this way, catalytically and adsorbtively inactive, however, surfaces that can be wetted with non-polar solvents are obtained. If against it If a more hydrophilic surface is desired, silanols may be preferred, in which the group R is an alkoxy group, an oxaalkyl group or a polyoxaalkyl group is. The technically easily accessible polyoxyethylene groups are particularly suitable as polyoxaalkyl groups significant.

The silanols of the general formula II are either known from the literature or are prepared according to standard processes known from the literature, for example by reacting dimethyldichlorosilane with alkylmagnesium analogides, the The group R to be introduced is alkyl radical, followed by hydrolytic cleavage of the second chlorine atom. Another standard procedure is the implementation of, for example Dimethycnlorsilan with a 1-alkene, in the carbon chain according to the Definition of the group R also CH2 groups can be replaced by oxygen atoms, again followed by hydrolytic cleavage of the chlorine atom from the silicon.

The following examples illustrate the preparation of previously unknown Silanols of the general formula II: Preparation example A (a) By dropwise addition of 82.5 g of 1-bromohexane to 60 g covered with 150 ml of anhydrous diethyl ether Magnesium shavings, a solution of hexyl-1-magnesium bromide is made. These Solution is added dropwise to boiling point with stirring over the course of about 4 hours Given a solution of 193.5 g of dimethyldichlorosilane. The reaction mixture is then heated to boiling for -24 hours with stirring in a nitrogen atmosphere. The deposited precipitate is filtered off; from the filtrate the diethyl ether and the excess dimethyldichlorosilane are distilled off. The remaining hexyl- (1) -dimethylchlorosilane is then extracted under reduced pressure distilled; Kp16: 77-800C.

The following are produced in the same way: Propyl- (1) -dimethylchlorosilane, Kp720: 100-1100C; O decyl- (1) -dimethylchlorosilane, bp (0.5 Torr): 103-106 tetradecyl- (1) -dimethylchlorosilane, Bp (0.5 torr): 170-173 ° octadecyl- (l) -dimethylchlorosilane, m.p. 28-300C; 3- (2'-methoxyethoxy) propyl (1) chlorosilane, Bp 0.05: 60 ° C; 5- (2'-methoxyethoxy) pentyl (1) chlorosilane, boiling point 0.05: 100 ° C; (b) To one Mixture of 600 ml of diethyl ether, 3.6 g of water, 24.8 g of freshly distilled aniline and 200 ml of acetone becomes a solution of 35.8 g of hexyl- (1) -dimethylchlorosilane at 0 ° C. with vigorous stirring dripped into 200 ml of diethyl ether. The reaction mixture is then filtered and the filtrate was washed 6 times with 200 ml of water each time. The organic phase will then dried over sodium sulfate and evaporated. The residue will be in little Petroleum ether (boiling range 50-700C) added and over a column with 320 g of silica gel chromatographed. After elution with 3200 ml of petroleum ether, 750 ml of diethyl ether are added 28.0 g of hexyl- (1) -dimethylsilanol eluted; Bp 0.1 = 44-45 ° C.

The following are prepared in the same way: Propyl- (1) -dimethylsilanol, boiling point 13: 62 - 64 ° C; Octadecyl- (1) -dimethylsilanol, m.p. 51 ° C; 3- (2'-methoxyethoxy) propyl (1) dimethylsilanol, 20 nD 1.4400 4- (2'-methoxyethoxy) -butyl- (1) -dimethylsilanol, 20 nD 1.4405 5- (2'-methoxyethoxy) -pentyl- (1) -dimethylsilanol, 20 nD 1.4439 5,8,11,14,17-pentaoxaoctadecyl- (1) -dimethylsilanol, 20 1.4470 Manufacturing example B (a) To 2.43 g of magnesium turnings in 30 ml of anhydrous tetrahydrofuran are 21.1 g of 1-bromo-4- (2'-methoxyethoxy) butane was added dropwise so quickly that the temperature increases 400C remains. About 15 ml of tetrahydrofuran are then distilled off at normal pressure and 50 g of dimethyl diethoxysilane were added. The mixture is kept at 90 ° C for 24 hours stirred and then after cooling with a mixture of 200 ml of diethyl ether and 100 ml of aqueous ammonium chloride solution (10 percent by weight) are added. The ether phase is separated off, washed with water, dried over sodium sulfate and evaporated.

The residue is distilled under reduced pressure.

After separating off the excess dimethyl diethoxysilane 12.3 g of 4- (2'-methoxyethoxy) -butyi- (1) -dimethylethoxysilane were obtained; nD ° 1.4251.

D (b) A solution of 12.5 g of 4 (2'-methoxyethoxy) -butyl- (1) -dimethylethoxysilane in 60 ml of diethyl ether is mixed with a solution of 50 mg of ammonium chloride in 70 ml of water Thoroughly mixed for 20 hours. Then the ether phase is separated off with sodium sulfate dried and evaporated. The residue is taken up in a little hexane and taken over 120 g silica gel (grain size 62-200 microns) chromatographed.

After pre-eluting with 220 ml of a mixture of 95 parts by volume Hexane and 5 parts by volume of benzene are 10.4 g of 4- (2'-methoxyethoxy) -20 with 280 ml of diethyl ether butyl- (1) -dimethylsilanol eluted; nD 1.4405.

The reaction of the silanol of the general formula II with the hydrated According to the invention, the carrier material is carried out in such a way that an excess of the silanol is evenly distributed in the hydrated carrier material and the resultant The mixture is heated to a temperature between 50 and 4000C. The amount of too The silanol used can be determined in a simple manner from the specific surface area of the hydrated support material.

Assuming that the surface of the substrate is occupied with a maximum of 7 micromoles of silanol groups per square meter, and that the Concentration of dimethylsilyl groups because of their space filling 5 micromol / m2 not exceed kaiin, are used for the silanization according to the method according to the invention 4.5-100 micromoles of the silanol of the general formula II are used per square meter 10-30 are preferred for carrier materials with large specific surface areas Mikromoi / qm used. For carrier materials with a smaller specific surface Occasionally, even larger excesses, e.g. up to 1000 micromol / m2, are used. The specific surface of the carrier material to be silanized is determined according to standard methods, for example determined by the BET method.

For even distribution of the silanol in the hydrated carrier material it is in a small amount of a suitable, inert organic solvent, for example petroleum ether, cyclohexane, hexane, diethyl ether or carbon tetrachloride dissolved and the carrier material thoroughly mixed with this solution. Afterward the solvent is distilled off again, expediently under reduced pressure. If one uses silanols which are sufficiently high at the reaction temperature Vapor pressure can be applied to spreading using a solvent also be waived. The resulting mixture of the carrier material and the silanol the general formula II is then heated to the desired reaction temperature. One Temperature of 100-4000C, in particular 240-3400C, is preferred. The heating can be done in an open or closed vessel. If a silanol of Formula II is used, which already has one at the desired reaction temperature has a noticeable vapor pressure, a closed vessel is preferable for heating. The duration of the heating depends on the reactivity of the selected silanol Formula II dependent and is usually 0.5-100 hours. Preferably be the mixtures of carrier material and silanol 1 to 40, in particular 2 to 24 hours.

heated to the desired reaction temperature. The heating can be done in Vacuum or in the presence of air or an inert gas such as nitrogen or argon be performed. In an inert gas, especially at high reaction temperatures worked to an oxidation of the organic residues of the sflanol by air as possible to exclude. Occasionally it has proven advantageous to add the reaction mixture a catalytic amount of a volatile base such as ammonia, hydrazine, or one to add organic amines such as methylamine, ethylamine, aniline or pyridine. Through this satisfactory degrees of conversion are achieved even at reaction temperatures between 50 and 2000C, preferably 80-1500C. This variant of the process is special advantageous when reacting with thermally sensitive or sterically hindered Silanols of the general formula II used.

Upon completion of the heating, the reaction mixture becomes inherent freed in a known manner from the excess silanol of the general formula II. Preferred this is done by an exhaustive extraction with an inert organic Solvent in which the silanol and any reaction products formed therefrom such as, for example, disiloxanes are sufficiently soluble. To have been particularly suitable Hydrocarbons such as petroleum ether, gasoline, benzene or toluene are halogenated Hydrocarbons such as chloroform, carbon tetrachloride or trichlorethylene as well Ether like Diethyl ether or tetrahydrofuran proved. Such a one Extraction can be done by washing it out thoroughly once; occasionally can it may be necessary to place the Urasetzur.gsprodukt in a Soxhlet apparatus for up to 24 hours with the chosen solvent to extract all the remnants of the excess To remove silanol and its reaction products.

The products produced by the process according to the invention are in the same way as the silanized ones obtained in known silanization processes Carrier materials used; a particularly preferred application of the invention manufactured products is used as support materials for stationary phases in the Gas chromatography.

The following examples serve to illustrate the invention Procedure: Example 1 250 g of finely divided silicon dioxide with a specific 2 surface area of 190 m / g are 3 weeks in a water vapor saturated Then the material so hydrated is left to stand for 5 days freed from adsorbed water at 80 ° C. and 10 5 mm Hg, 2.5 g of the hydrated Finely divided silicon dioxide with a solution of 1.06 g of 4- (2-'Methoxyäthoxy) -butylb dimethylsilanol in 50 ml of hexane mixed thoroughly. The mixture is reduced under reduced pressure Freed from pressure of solvent, the white, powdery residue in a glass ampoule transferred and melted down at 0201 mm Hg, the ampoule is then open for 5 hours Heated to 3000C. After cooling, the contents are placed in a Soxhlet apparatus for 24 hours extracted with diethyl ether and then dried at 0.01 mm Hg and 80 ° C for 3 hours. The product has a content of 5.69% C and 1223% H; from this is calculated a coverage of the surface of the silicon dioxide carrier material with 3.07 micromoles / m2 4- (2'-methoxyethoxy) butyl- (1) -dimethylsilyl groups.

Example 2 1.0 g of the hydrated as described in Example l Very finely divided silicon dioxide are mixed with a solution of 0.66 g of octadecyl (l) -dimethylsilanol Thoroughly mixed in 20 ml of petroleum ether. After evaporation of the solvent is the powdery material in a 25 ml glass ampoule in a vacuum for 24 hours heated to 200 ° C. Then, as in Example 1, it is extracted with diethyl ether and dried.

The result of the elemental analysis gives an occupancy of the support material with 3.01 micromoles / m2 of octadecyl (1) dimethylsilyl groups.

Example 3 1.0 g of the hydrated as described in Example 1 Very finely divided silicon dioxide are mixed with a solution of 0.45 g of 4- (2'-methoxyethoxy) -butyl- (1) -dimethyl-silanol thoroughly mixed in 20 ml of cyclohexane. After evaporation of the solvent, the powdery material in a 25 ml glass ampoule in a vacuum at 350 ° C. for 4 hours then heated as in Example 1, extra hiert with diethyl ether and dried. The result of the elementary analysis shows an occupancy of the carrier material with 3.31 micromoles / m2 of 4- (2'-methoxyethoxy) -butyl- (1) -dimethyl silyl groups, example 4 1.0 g of the finely divided silicon dioxide hydrated as described in Example 1 be thoroughly with a solution of 0.25 g propylb dimethylsilanol in 20 ml hexane mixed. After evaporation of the solvent, the powdery material is in a 25 ml glass ampoule at normal pressure under nitrogen for 5 hours at 300 ° C heated. Then, as in Example 1, it is extracted with diethyl ether and dried. The result of the elemental analysis shows an occupancy of the carrier material with 3.71 micromoles / m2 propyl- (l) -dimethylsilyl groups.

Example 5 23.2 g of that hydrated as described in Example 1 Finely divided silicon dioxide with a solution of 10 g De-zYlZ dimethylsilanol Thoroughly mixed in 150 ml of hexane, then the solvent is added diminished The pressure is distilled off and the RUckstarXd is filled into a 500 ml glass ampoule. After evacuating to 0.01 mm Hg, the ampoule is filled with ammonia to a pressure of about 200 mm Hg, melted and heated to 1000C for 24 hours. Afterward the contents are washed for 24 hours with 1 1 of diethyl ether and then at 1000 and C, Ol mm Hg dried. The product contains 9.44% carbon, which corresponds to one Occupancy with 3.96 micromoles / m2 of decyl- (l) -dimethylsilyl groups.

Example 6 2 A 4 mm thick, 25 cm large plate made of hard, acid-resistant Instrument glass is left to stand in concentrated nitric acid for 3 days. Afterward the plate is rinsed with distilled water, acetone and diethyl ether.

The plate prepared in this way is immersed in a solution of 4% by weight decyl- (1? -Dimethylsilanol in pentane, briefly air-dried and heated in a closed vessel in a nitrogen atmosphere for 10 hours at 2500 ° C. After cooling, the plate is with Diethyl ether rinsed, the result of the treatment according to the invention becomes visible when examining the wettability of the glass surface with liquid hydrocarbons. While the untreated plate is not wetted by hydrocarbons with 11-15 C atoms (contact angle plate / wetting liquid: 00), silanized plate measured the following wetting angle: Hydrocarbon contact angle Undecan 00 Dodecanese 50 Tridekan 120 Tetradecan 140 Pentadecan 170 The treatment according to the invention thus achieves the wettability of the surface by hydrocarbons with 12-15 carbon atoms.

Example 7 130 g of wide-pored silica gel with a specific surface area of about 7 m2 / g is left to stand under water for 24 hours.

After filtering, first in air, then at 0.01 mm Hg and 1000C dried. The silica gel hydrated in this way is dissolved in a solution of 1.97 g Decyl- (1) -dimethylsilanol registered in 300 ml of diethyl ether, mixed, and the Ether distilled off under reduced pressure at 50 ° C. Then the silica gel heated in a round bottom flask of 500 ml for 3 hours at 0.01 mm Hg at 50 ° C, the flask is filled with ammonia at a pressure of 500 mm Hg, melted shut and Heated to 100 ° C for 24 hours. After cooling, the contents of the flask are placed in a Soxhlet apparatus Extracted for 3 hours with diethyl ether and then dried at 80 ° C. and 0.01 mm Hg. The product contains 0.50% C; - an occupancy of the upper surface is calculated from this of the carrier material with 4.96 micromoles / m2 of decyl- (1) -dimethylsilyl groups.

Example 8 1.0 g of the hydrated as described in Example 1 finely divided silicon dioxide is in a solution of 0, (4 g 5,8,11,14, 17-pentaoxaoctadecyl (1) -dimethyl-silanol suspended in 20 ml of ether. After evaporation of the solvent the powdery material is placed in a 25 ml glass ampoule in a vacuum for 8 hours heated to 250 °. Then, as in Example 1, extraction is carried out with diethyl ether and dried.

The result of the elemental analysis (C%: 7.82) shows an occupancy of the material with 2.65 micromoljm2 5,8,11,14,1 7-pentaoxaoctadecyl- (1) -dimethylsilyl groups.

The product is hydrophilic. For example 9 1.0 g of the same as in Example 1 described hydrated, finely divided silicon dioxide is mixed with a solution of 0.29 g of phenyldimethylsilanol in 20 ml of n-hexane is mixed thoroughly. After evaporation of the solvent, the powdery material is placed in a 25 ml glass ampoule in an ammonia atmosphere (500 mm Hg) heated to 1000C for 24 hours. Then will extracted analogously to Example 1 with diethyl ether and dried. From the result of the Elemental analysis (C%: 4.92) shows an occupancy of the carrier material of 2.89 Micromoles / m2 of phenyldimethylsilyl groups.

Example 10 1.0 g of the hydrated as described in Example 1, Finely divided silicon dioxide is mixed with a solution of 0.39 g of decyl- (1) -dimethylsilanol thoroughly mixed in 20 ml of n-hexane. Then the solvent becomes complete removed and the residue filled into a glass ampoule.

Then 10 mg of pyridine are added to the residue. the ampoule is evacuated to 0.01 mm Hy while cooling with liquid air, melted and Heated to 1000C for 24 hours.

The contents are then treated with diethyl ether in a Soxhlet apparatus for 2 hours extracted and then dried at 1000C and 0.01 mm H9. The product contains 7.47% Carbon corresponding to an occupancy of 3.04 micromol / m2 Deyxl- (1) -dimethylsilyl groups.

Example 11 5.0 g of the hydrated as described in Example 1 Finely divided silicon dioxide and 0.9 g of trimethylsilanol are evacuated in a Glass ampoule heated to 4000C for 16 hours. Then, as in Example 1, with Diethyl ether extracted and dried. The product contains 2.05% C; calculated from this a coverage of the surface with 3.12 micromol / m2 trimethylsilyl groups.

Claims (4)

Claims 1. Process for the silanization of carrier materials based on silicon dioxide by reaction with silanols, characterized in that the carrier material is hydrated by the action of water or steam, an excess of one or more silanols of the general formula II where R1 and R2 are identical or different and are methyl or ethyl, and R is an alkyl or alkoxy group with 1-25 C atoms in which one or more non-adjacent CH2 groups are optionally replaced by oxygen atoms, or a phenyl group means, allowed to act in the absence of a solvent at a temperature between 50 and 450 ° C., optionally in the presence of a volatile base, and then the excess silanol is removed in a manner known per se. 2. The method-according to claim 1, characterized in that the Act silanol of general formula II at 80 - 1500C in the presence of ammonia leaves, 3. Process according to claims 1 or 2i, characterized in that one 10-30 micromoles of silanol of the general formula II per square meter of surface area of the Can act on the carrier material. 4. The method according to claims 1 to 3, characterized in that that the action of the silanol is carried out in a closed system.